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Donald Trump ran a brilliant Republican primary campaign. The problem? He's running that exact same campaign in the general election.

Trump cruised to the Republican nomination on the strength of his hard-line stance on immigration (build wall, make Mexico pay for it) and his willingness to savage the other 16 people running against him ("Low energy" Jeb Bush, "Little Marco" Rubio, "Lyin" Ted Cruz).

More than 13 million people cast a vote for him in the Republican primaries. That was almost double what the second place finisher - Cruz - won.

The problem if you are a Republican is that Trump appears to not only have learned lots of wrong lessons from that winning campaign but also that he seems to not grasp that the way you win a primary is very different from the way you win a general election.

"You think I'm going to change?" Trump asked reporters rhetorically in a news conference late last month. "I'm not changing."

In Trump's mind, his willingness to be politically incorrect - whether it's raising questions about the Mexican heritage of a federal judge overseeing a case involving Trump University attacking Mitt Romney, the 2012 Republican presidential nominee, as having "choked like a dog" or repeatedly referring to Senator Elizabeth Warren as "Pocahontas" - is a winning formula.

And those are just things Trump has done in the past three weeks!

If it worked in the primary, it'll work in the general: That's the Trump logic. The problem with that? Well, there are lots of issues with it, but the main one is this: The general electorate is significantly larger and more diverse than in a Republican primary.

As I mentioned above, Trump got more than 13 million votes in the Republican primary process: 13.3 million to be exact, according to RealClearPolitics.

Now, compare that to how many votes Mitt Romney, aka the choking dog, got in the 2012 general election: 60.9 million. And Romney lost - convincingly - to President Barack Obama, who got nearly 66 million votes.

Romney's popular vote numbers are no outlier. John McCain got nearly 60 million votes while being crushed by Obama (69 million votes) in 2008. George W. Bush got 62 million votes in his 2004 re-election win.

It's a reasonable assumption then that Trump will need at least 60 million votes to win the White House in November - and almost certainly north of 65 million given population growth in the country.

That's roughly five times the number of votes he received in the primary. Much of that delta will be made up by the fact that lots and lots of Republicans simply don't vote in GOP primaries but will almost certainly turn out in a general election - even if it's only to cast a vote against Hillary Clinton.

But, assuming what worked to win you 13 million votes is a sure-fire recipe for winning you five times that number seems to be a decidedly shaky proposition.

Why? Because we know from recent presidential history that the electorate of a Republican primary is whiter and older - by a considerable amount - than the general electorate.

Let's, for example, take a look at the swing state of Florida, which also happened to be one of Trump's strongest states in the primary process.

Trump will need at least 60 million votes to win the White House in November. That's roughly five times the number of votes he received in the primary.

In the Florida GOP primary in March, 74 per cent of voters were 45 or older. Seventy-eight per cent were white, while 16 per cent were Latino and 3 per cent were black.

In the 2012 Florida race between Obama and Romney, which the incumbent won by one percentage point, just 61 per cent of voters were 45 or older. Sixty-seven per cent were white, while 17 per cent were Latino and 16 per cent were black.

(Nationally in 2012, 54 per cent of the electorate was 45 or older. Seventy-two per cent was white, compared to 13 per cent who were African American and 10 per cent who were Latino.)

It doesn't take a mathematician to see why those differences between a primary voter pool and a general electorate are problematic for Trump.

In the latest Washington Post-ABC News poll conducted in May, Clinton led Trump 47 per cent to 39 per cent among voters ages 18 to 39. Among non-white voters, her edge was massive: 69 per cent to 21 per cent.

Trump appears to either be ignorant of or simply willing to ignore the vast differences between what can be a winning formula in a Republican primary and what adds up to a majority in a general election in 2016.

That's something that deeply worries Republican elected official trying to hold fast to their majorities in the House and the Senate. If Trump continues to run a Republican primary campaign masquerading as a general election campaign, it might not only cost his party the White House but their majorities in Congress as well.